In April, 2008, GdT was officially announced as director, with plans to spend four years in NZ. No release schedule mentioned, and it's unclear when this period was to start/started, though the article said he wasn't leaving "immediately" (HBII was scheduled to open in July).

Prior to that, dates of 2010/2011 had been mentioned, but the GdT announcement was delayed by the writer's strike, and in the various 2008 discussions it was assumed that it would slip to 2011/2012.

Assuming the del Toro family (he was talking about the whole family going) moved in fall/winter 2008, 4 years would be fall 2012. And it's been recently mentioned that he'd been there 2 years.

If the current release schedule is now 2012/13 (which seems plausible) and he had to be there the whole time, 2008-2013 would be 5 years, not six. But it isn't green-lit yet, so ...

My guess is they're all throwing numbers off the tops of their heads and it isn't worth trying to pin down too much. Bottom line: it's going to be a lot longer than originally planned, and GdT is a director in great demand who can't afford to sit on the shelf.